Combined carrier and radio system



H. A. AFFEL. COMBINED CARRIER AND RADIO sYsTEr'h.

- APPLICATION F!LED SEPR 30. I919.

Patented Sept. 21, 192% 2 SHEETS-SHEET I.

INVENTOR.

v ORNEY.

H. A. AFFEL.

COMBINED CARRIER AND RADIO SYSTEM. APPLICATION mm SEPT-30,1919.

Patented Sept. 21, 1929.,

VINVENTOR.

STA 1a HERMAN A. AFFEL, OF BROOKLYN, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONE I AND TELEGRAPH COMPANY,. A CORPORATION OFNEW YORK.

x COMBINED CARRIER AND RADIO SYSTEM.

1 1,353,698. Spwficatwn of Letters Patent Patented Sept. 21, 1920.

v Application filed September 30. 1919. Serial No. 327,458.

T all whom it may concern Be it known that I, HERMAN A. AFFEL, residin at Brooklyn, in the county of Kings and tate of New York, have invented certain Improvements in Combined Carrier and Radio Systems, of which the following is a specification.

This invention relates to a signaling system and more particularly to arrangements for combining a wire carrier system with a radio system.

One of the features of this invention relates to the provision, in a system, in which a plurality of signals may be simultaneously transmitted over a common circuit by means of carrier currents, of means for relating the carrier system to a radio system in such a manner that the carrier frequencies which.

are ordinarily too low for radio transmission may bestepped up to radio frequency.

Another. feature of the invention relates to a signaling system in which low frequency signaling currents are transmitted in a low frequency condition to a station at which they are translated into carrier currents and as such transmitted over a wire line to a radio station, where they are again translated into higher frequencies for radio transmission, the system being also arranged so that the converse frequency translation takes place for transmission in the opposite direction.

The inventionmay now be more fully understood from the following description when read in connection with the accompanying drawing, Figure 1 of which is a schematic diagram of one embodiment of the invention and Fig. 2 of which is a schematic diagram of the carrier terminal apparatus constituting one of the elements of the invention.

Referring to Fig. 1, ML designates a main carrier transmission line extending from a carrier station at which terminal carrier apparatus X is located, to a radio station Y. At the radio station the line ML is associated through a transformer with a radio receiving clrcuit RL and with a radio transmitting circuit TL. An artificial line .-.or network MN is provided for balancing the line ML, thereby rendering the circuits TL and RL substantially conjugate.

The circuit TL is associated with the transmitting antenna AT, through a transformer and includes a modulator M and as a duplex vacuum tube modulator of the general type disclosed in the U..S. application of. John R. Carson, Serial No. 157 ,413,

dated March 26, 1917. This modulator is supplied with carrier currents of radio frequency'from a source G, which may be of any suitable character and is so arranged that normally the carrier frequency is suppressed, but when the band of modulating currents is supplied to the circuit TL, the carrier frequency from the source G ismodulated by the modulator M, so that a double band of frequencies appears in the output circuit of the modulator M. The band filter BF is preferably of the general type disclosed in the U. 9.. patents to George A; Campbell, Nos. 1,227,113 and 1,227,114, is sued May 22, 1917. This filter may be so designed as to transmit one of the side bands, preferably the upper, and suppress the other, so'that the modulator in conjunction with the band filter BF, operates to step up the band of carrier frequencies supplied to the circuit TL to a band of equal width, but of radio frequenc The receiving circuit RC is associated with the receiving antenna AR through a transformer 21 and includes a band filter BF, an amplifier A, detector D and band filter BF. The band filter BF is similar to the filter" BF and'is designed to pass a frequency band of the same width, but

where, as is usually the case, radio transmission and reception take place at different frequencies, this band will be' sufficiently separated from the band transmitted by the filter BF to provide for frequency discrimination between oppositely directed transmissions The amplifier A may be of any well known type, but as illustrated is an ordinary vacuum tube amplifier. The detector 1) is preferably a duplex vacuum tube detector of the type disclosed in the U. S. application of John R. Carson, Serial-No. 157 ,414, dated March 26, 1917. In accordance with the well known principles of homodyne detection, this duplex detector is supplied from the generator G, with oscil- .lations ofthe basic radio frequency assigned to. the receiving channel, whereradio transmission and reception are to take place at different frequencies the frequency supplied to the generator G will be different from that iIO supplied to the generator G and Will be so chosen that when combined with the band transmitted through the filter will be stepped down in the in the frequency spectrum, as

of frequencies BF, the band same position the band transmitted over the main line ML. The filter BF is also of the Campbell type .ciated, through a balanced transformer 10,

with common transmitting and receiving circuits TL and RL, respectively, which are rendered conjugate wit-h respect to each other by balancing the main line ML with the artificial line MN in a well known man.- ner. A plurality of low frequency signaling lines L L L5 and L are associated with the transmitting and receiving circuits TL and RL through transmitting channels TL TL etc. and receiving channels RL R11 etc. The apparatus associated with the transmitting and receiving channels corresponding to each low frequency line is in general similar and a description of the apparatusin one instance will suffice for all. For example, the transmitting channel TL which is rendered conjugate with respect to the receiving channel BL, by means of the usual balanced transformer H. and artificial line l\' includes a mammal-e1 band filter TF amplifier TA, and band filter TF The modulator M, will be similar to the modulator M of Fig. 1 and is supplied with carrier currents of the basic frequency assigned to this channel which, for purposes of illustration, is indicated as being 25,000 cycles. The filter Tl in the output circuit of the modulator M is a band filter of the Campbell type, adapted to transmit carrier frequencies, but suppresses low frequency components. The amplifier TA, may be an amplifier of any type, but is preferably a. vacuum tube amplifier. The band filter TF, is of the Campbell type and is so designed as to transmit one of the side bands resulting from the modulator of the carrier fre'uiency by low frequency signaling current: while suppressing the other.

The receiving channel FL, includes a filter RF, a detector 1 an amplifier RA, and a filter RF, The band filter RF, is similar to the band filter TF, and may be arranged to transmitthe same band of frequencies. The demodulator D, is preferably of the same type as the demodu ator D of Fig. l and is supplied with homodyne currents of the carrier frequency assigned to the channel, which, as above stated, may

' 1*, F F, and F respectively, to amplifiers The amplifier RA, may but is preferably The filter RF be 25,000 cycles. be any type of amplifier, a vacuum tube amplifier. may be a so-called low pass filter of the Campbell type and is designed to transmit a band of frequencies extending from Zero up to the upper frequency employed in low frequency signaling. If the signaling cur rents to be transmitted are voice currents, the upper limit of this filter may be in thzc neighborhood of 2,000 cycles.

Similar apparatus is associated with the transmitting and receiving channels of the other low frequency lines, the only essential difference being that the frequencies assigned to the channels are different. In the case indicated, the frequency 20,000 cycles is assigned to 'the channels associated with the lin L 15,000 cycles to the channels associated with the line L, and 10,000 cycles assigned to the channels associated with the line L I In order to produce these carrier frequencies a basic frequency may be generated by means of any suitable enerator such as a. vacuum tube oscillator The basic frequency generated is, for purposes of illustration, indicated as above 5,000 cycles. A harmonic producer H, which may be a dis torting tube arrangement of the character disclosed in the U. S. application of P). N. Kendall, Serial No. 139,530 filed December 29, 1916, is provided for the purpose of producing harmonics of the fundamental frequency. The second, third, ffiourth and fifth harmonics are indicated as being supplied through filtering circuits A,, A AT, and A liese filtering circuits may be either Campbell filters or ordinary tuned circuits, but are preferably the latter. The harmonics, after being amplified to the desired value, are then supplied to the modulators and demodulators of the transmitting and receiving channels.

Further details of the apl'iaratus maybe understood from a description of the operation which is as follows: Low frequency signals incoming from the lines L, L. L, and L, are transmitted by the transmitting channels TL, TL TL, and TL, and impressed upon the modulators M M M, and M The modulated carrier currents are then passed through the filters TF TF l1, and TF amplified by the amplifiers TA TA TA, and TA, and then passed through the filters TF,, Tl TF', and Tl, These filters suppress one of the side bands in each channel, for instance, the upper side band, and transmit the other, so that the four bands are impressed upon the common trans- Lmodulated at the cuit TL and modulate the radio frequency supplied to the modulator M, thereby producing two side bands of radio frequency in the output circuit of said modulator. The band filter BF suppresses the lower side band and transmits the upper, which is then radiated by the antenna AT.

A band of radio frequencies received by the antenna AR is passed through the band filter BF and amplified by the amplifier A. The amplified band is then impressed upon the demodulator D and upon beating with the radio frequency supplied by the source G appears in the output circuit of the detector D as two side bands, one stepped up with respect to the band receivedby the an tenna and one steppeddown in frequency with respect to said band. The band filter BF suppresses the upper band and transmits the lower side band, which is then transmitted through main line ML. After being transmitted over said main line, the received carrier frequencies are transmitted through the transformer 10 into the common receiving circuit RL and are selected by the filters RF The received modulated frequencies are then impressed upon the detectors 1),, D D and D and by the homodyne action of the detectors the low frequency signals in accord ance with which the radio frequencies were distant transmitting sta- :tion, appear in the output circuits of the degiectors. These low frequency currents are amplified by the amplifiers RA RA RA and RA, and after being passed through the filters RF RF,,- etc. are transmitted to the lines L I1 L and L respectively.

It will be understood that the frequencies referred to in the preceding description and indicated on the, drawing are merely illustrative and that in practice otherfrequencies maybe used, as conditions may require. It will also be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated, without departing from the spirit of the invention as defined in the following claims.

the transformer 10 to the RF etc. into the corresponding receiving channels,

What I claim is: 1. In a signaling system, a plurality of low frequency signaling lines incoming to a carrier station, means at said carrier station for translating signals from, sald hnes into carrier currents, a carrier transmission line upon which said translated signals maybe superposed, said carrier line extending from said carrier station to a radio station, and means at said radio station for translating said carrier frequencies into radio frequencies for transmission over said carrier line to said carrier station, a plurality of low frequency signaling lines incoming to said carrier station, andmeans at said station for translating the carrier frequencies transmitted over said carrier line into low frequency signals for transmission to said low frequency lines.

4. In a signaling system, a'radio receiving station, means at said station to translate radio frequencies into carrier frequencies, a carrier transmission line extending from said radio receiving station to a distant carrier'station for transmitting said carrier frequencies to said carrier station, and

means associated with.

'cies for radiation to a distant radio receivmeans at said carrier station to translate said carrier frequencies into low frequency signaling currents.

In testimony whereof, I have signed my name to this specificationthis 29th day of September 1919.

HERMAN A. AFFEL. 

